a) Field of the Invention
The invention is directed to a veterinary syringe with a dosing device for administering medications in different preselectable amounts. This veterinary syringe substantially comprises a piston rod which projects into a syringe cylinder by a piston provided at the first end of the piston rod and which is supported at a handle by its other end by means of an actuating lever which is fastened to the other end so as to be swivelable. The piston rod is supported so as to be displaceable longitudinally in a holder which is rigidly connected with the handle. The dosing device is provided between the holder on one side and the piston rod on the other side.
b) Description of the Related Art
In known veterinary syringes with preselectable dosing for administering different amounts of medication, there is an actuating lever for dispensing the medication from the syringe cylinder. The actuating lever is connected with the piston rod in an articulated manner on one side and is fastened to a handle via a joint on the other side so as to be swivelable, this handle being rigidly connected with the holder of the veterinary syringe. The relative motion between the piston rod and syringe cylinder is achieved in that the actuating lever is swiveled against the handle by force applied by hand and the piston is accordingly pressed into the syringe cylinder. In so doing, the force of a spring element must also be overcome; when the force exerted by the hand is reduced, this spring element brings the actuating lever back into the starting position and accordingly brings the piston rod and the piston back into the end position. A dose amount is preselected by means of a slide which is fastened to the holder and is movable vertically to the axis of the piston rod, wherein three catch positions are possible: one catch position on each side of the center of the piston rod, and a middle position.
While the slide allows the piston rod free passage in the middle position, so that the entire amount of medication located in the syringe cylinder can be ejected, the free path of the piston rod is limited in the side catch positions in that a stop which is arranged at the slide and has a protuberance or a recess (depending on construction design) engages at the piston rod and prevents the piston rod from sliding in farther.
Three different dose amounts can be preselected with this veterinary syringe. However, it is disadvantageous that the number of catch positions (left, middle, right), and thus also the dosing amounts that can be preselected, is thereby exhausted. Further, a relatively large expenditure of force in a direction transverse to the handle and to the actuating lever is required to switch from one dosing amount to another, so that the handling of the preselecting mechanism is unfavorable in ergonomic respects. Moreover, this type of slide construction is soiled very easily so that switching becomes increasingly difficult.